1. The Mole

2. Diatomic elements
– elements that do not exist on their own, they must be in a covalent bond with themselves to be more stable.

3. N2 O2 F2
Cl2
Br2 I2 H2

4. Dimensional Analysis Review
How many seconds are in 5.0 hours?
5.0 hr
5.0 hr x 60 min x 60 sec = sec
1 hr min

5. Dimensional Analysis Review
Calculate the number of inches in 26 yards
26 yards
26 yards x 3 ft x 12 inches = 940 inches
1 yd ft

6. The Mole
Chemists need a convenient method for counting accurately the number of atoms, molecules, or formula units in a sample of a substance.
The mole, commonly abbreviated mol, is the SI base unit used to measure the amount of a substance.

7. A mole is used to represent the amount of a substance or compound.
H2 means 1 mole of H2
NaCl means 1 mole of NaCl.
Hydrates – compounds that contain water. Written as NaCl • 2H2O

8. The Mole
A mole of anything contains 6.02 x 1023 representative particles.
A representative particle is any kind of particle such as atoms, molecules, formula units, electrons, or ions.
6.02 x 1023 is called Avogadro’s number

9. Molecular or Formula Mass Calculations
You have to add up the masses of every element found in the compound or molecule.
Ex. (NH4)3PO4 Ammonium Phosphate

10. Make a list of how many of each element you have.
P = 1
O = 4

11. Multiply how many of each element you have by their mass
Multiply how many of each element you have by their mass. (Look it up on the periodic table.) Then add up the total. The units always grams.

12. N = 3 x 14 = 42
H = 12 x 1 = 12
P = 1 x 31 = 31
O = 4 x 16 = 64
149 g

13. example
NaCl
Na = 23g
Cl = 35 g
Total 58 g

14. Hydrates-
are just a molecule or compound that has a certain number of water molecules attached to it.
They are written like NaCl • 5H2O.

15. When you are asked to calculate the mass you have to understand that there are 5 H2O molecules attached to 1 NaCl.
That means: 10 H & 5 O in addition to the Na & Cl.

16. H = 10 x 1 = 10
O = 5 x 16 = 80
Na = 1 x 23 = 23
Cl = 1 x 35 = 35
Total amu or grams

17. Conversion Factor # 1 1 mole Molecular weight (g)
The molecular mass comes from the periodic table!

18. Mole – Mass Calculations
What is the mass of 4.21 moles of iron (III) oxide?
Start with your given:
4.21 moles Fe2O3
Draw your line
4.21 moles Fe2O3 x _____________

19. Mole – Mass Calculations
Place conversion factors
4.21 moles Fe2O3 x g Fe2O3
1 moles Fe2O3
Cross out units & work the problem
672 g Fe2O3

20. Another Example Calculate the mass of 1.630 moles of Na
1.630 moles x 22.9g
1 mole
37.47 g Na

21. Mole – Mass Calculations
How many moles of Ca(OH)2 are in 325 grams?
325 g x 1 mole
74 g
4.39 moles Ca(OH)2

22. Another Example How many moles are in 62.17 g of sodium chloride?
62.17g x 1 mole
58 g
1.064 mol NaCl

23. Conversion Factor #2

24. Representative Particles
Anything - Representative particles
Elements – Atoms
Covalent Compounds – Molecules
Ionic Compounds – Formula Units
Ions - Ions

25. Mole – Representative Particle Calculations
Calculate the number of atoms in 3.50 moles of copper
Start with your given
3.50 mol Cu
Draw your line
3.50 mol Cu x _________

26. Mole – Representative Particle Calculations
Place the conversion factors
3.50 mol Cu x 6.02 x 1023 atoms
1 mol Cu
Work the problem
2.11 x atoms Cu

27. Another Example Calculate the number of molecules in 2.6 moles of H2O
2.6 mol H2O x 6.02 x 1023 mlcs = 1.6 x 1024
1 mol H2O mlcs H2O

28. Another Example
Calculate the number of formula units in 5.23 moles of NaCl
5.23 mole x x f. units
1 mole
3.15 x formula units NaCl

29. Mole – Representative Particle Calculations
How many moles of MgO are in
9.72 x molecules of MgO?
9.72 x mlcs x 1 mole
6.02 x mlcs
1.61 moles MgO

30. Another Example How many moles are in 4.50 x 1024 atoms of Zinc?
4.5 x 1024 atoms x 1 mole
6.02 x atoms
7.48 moles Zn

31. Mass – Particle Conversions
How many atoms of gold are in 25.0 g of gold?
25.0 g Au x 1 mole Au x 6.02 x 1023 atoms Au
g Au mole Au
7.65 x 1022 atoms of Au

32. Mass – Particle Conversions
How many grams of He are in 5.50 x 1022 atoms of He?
5.50 x atoms x 1 mole x g
6.02 x atoms mole
0.366 g He

33. example How many formula units are in 35.6 g of NaCl?
3.70 x formula units

34. moles Al2S3 means you have 1 mole of the compound Al2S3.
It is composed of 2 moles of Al atoms and 3 moles of S atoms

35. Ions in a compound How many Cl- ions are there in 35.6 g of AlCl3?
35.6 g AlCl3 x 1 mole AlCl3 x 3 mole Cl3 x x ions
132 g mole AlCl mole Cl3
Remember ions is just a word, atoms particles, representative units. Anything works

36. % Composition, Empirical Formulas, & Molecular Formulas

37. % composition
Mass of the element x 100
Mass of the compound

38. % composition- gives the relative mass of each atom in a compound.
Steps
1. Calculate formula mass of compound
2. Determine % of each atom
Ex: Calculate the % comp of N in NH4NO3
N x 2 = 28.0
H x 4 = 4.0
O x 3 = 48.0
80.0 g
% N = 28.0 g/ 80.0 g x 100 = 35%

39. Calculate the % composition of each atom in
a. Fe2O b. Ag2O c. HgO

40. % Composition Calculate the % Composition of iron (III) oxide
% Fe = 69.94%
% O = 30.06%

41. Molecular formulas- Used to tell exactly how many of each atom is present in the compound.
Empirical Formulas- The simplest formulas possible indicating the ratio of atoms found in the molecule. Think of it as reducing a fraction to the least common denominator.

42. Empirical Formula What is the empirical formula for H2O2? HO
What is the empirical formula for C6H12O6?
CH2O

43. C6H6
C2H2
C6H12O6
C4H10
P4O10
SO3
N2O4
NO2
Ag2C4H4O6

44. Empirical Formulas-calculations
The smallest whole number ratio of elements in a compound. It is determined by calculating the:
Calculate the moles present of each element in the compound.
Set up ratios for each element by dividing each mole amount by the smallest mole amount.
Use the ratio from step # 2 as the subscripts to write out the empirical formula.

45. Ex: Determine the empirical formula for a compound with 36. 5 % Na, 25
Ex: Determine the empirical formula for a compound with 36.5 % Na, 25.4% S, 38.1% O
Since each elements % adds up to 100% treat each % as a gram amount

46. Na = 36.5 g Na x 1 mole Na = 1.59 mole Na
S = g S x 1 mole S = mole S
32.1 g S
O = g O x 1 mole O = mole O
16.0 g O

47. Na S O
1.59 = = = 3.01
Ratio = 2:1:3
Na2SO3

48. Empirical Formula Problem
Calculate the empirical formula of a compound containing % S and % O.
40.05 g S x
59.95 g O x
1 mol S =
32.07 g S
1 mol O =
16.00 g O
1.249 mol
3.747 mol /
1.249 mol = 1
1.249 mol = 3
SO3

49. Ratio problems
Occasionally one part of your ratio will not be a whole number ( 1.5 : 1) It has to be!!!!!
Since H1.5O can’t exist you have got to fix it.
When this occurs you need to multiply by factor that will make it a whole # (like 2)
* what you do to one you must do to all, so every mole amount gets multiplied by 2!!

50. Empirical Formula Problem
Calculate the empirical formula for a compound containing g C, 8.16 g H, and g O.
48.64g x 1 mole C = mole/ 2.7 =1.5 x 2 = 3
12 g
8.16 g x 1 mole H = mole/2.7 = 3.02 x 2 = 6
1 g
x 1 mole O = 2.7 mole/2.7 = 1x 2 = 2
16 g
C3H6O2

51. Steps for Calculating Molecular Formula
Calculate the empirical formula
Get the molecular mass of the empirical formula that you just determined
Divide the experimentally determined molecular mass (given) by the molecular mass of the empirical formula
You will get a whole number
Multiply everything in the empirical formula by this number

52. Molecular Formula Problem
Calculate the molecular formula of a compound containing 40.68%C, 5.08%H, and 54.25%O with an experimentally determined molecular weight of g/mol

53. Molecular Formula Problem
40.68g C x 1 mol C = / = (1)2 = 2
12.01 g C
5.08g H x 1 mol H = 5.04 / = (1.5)2= 3
1.01 g H
54.25 g Ox 1 mol O = / = (1)2 = 2
16.00 g O
C2H3O2

54. Molecular Formula Problem
C2H3O2
Molecular Mass = 59.04
EDMM / EFMM = / = 2
Molecular Formula
C4H6O4

55. Molecular Formula Problem
Calculate the molecular formula of a compound containing g C, 3.64 g H, and g O with an experimentally determined molecular mass of g/mol
C12H9O6

56. Stoichiometry
Stoichiometry is just a long word for changing units in chemistry
Just remember to ALWAYS start with your given!
If you can do Dimensional Analysis, you can do stoichiometry